Scanning probe microscopy, also known as atomic force microscopy, is a way to study force interactions between a probe and sample surface. It is broadly used to visualize features on a sample surface that have dimensions from hundreds of microns down to sub-nanometer scale.
In atomic force microscopy, a probe attached to a cantilevered member responds to forces that result from proximity or contact with some sample surface. This force affects the tip's motion. The tip's motion therefore provides a measure of the force.
By scanning the probe's tip across the surface of a sample, one can obtain values of the extent of deflection as a function of spatial position. This allows one to build a two-dimensional map showing values of some surface parameter.
A difficulty that arises is that building such a map takes time because an entire region needs to be scanned. An obvious solution to the problem of slow scanning is to scan faster. But a cantilever arm has its own resonance characteristics. When one scans faster, the output signal of the microscope becomes a superposition of three components. The first component consists of the deflections caused by slow mechanical interaction with the surface. The second component consists of various second-order effects, such as deflections that arise from all other sources, including those that arise from the dynamic properties of the cantilever arm itself, and/or from the sliding interaction between the AFM probe and sample surface. The third component consists of instrumental and environmental noise.
From the combination of these three components, one can filter out an output signal. However, this filtering process is not perfect. As a result, the output signal can show artifacts that impair the accuracy of the measurement. To minimize formation of such artifacts, it is known to slow down the scanning. But this results in undesirable excessively slow scanning.